Specifications

22
Near-infrared light, which spans from 700 nanometers (nm) up to about 1000 nm, is beyond
what the human eye can see, but most camera sensors can detect it and make use of it. During
the day, a day and night camera uses an IR-cut lter. IR light is ltered out so that it does not
distort the colors of images as the human eye sees them. When the camera is in night (black and
white) mode, the IR-cut lter is removed, allowing the camera’s light sensitivity to reach down
to 0.001 lux or lower.
Figure 2.3a The graph shows how an image sensor responds to visible and near-IR light. Near-IR light spans the
700 nm to 1000 nm range.
Figure 2.3b Image at left, IR-cut lter in a day/night network camera; middle, position of IR-cut lter during day-
time; at right, position of IR-cut lter during nighttime.
CHAPTER 2 - NETWORK CAMERAS